The present invention relates to a reaction vessel which receives a solution. Heat is applied to the vessel to heat the solution and thereby create a reaction. After the reaction is complete and the contents of the reaction vessel are withdrawn, the reaction vessel is disposed of as a waste product.
Certain processes require the application of heat to a solution, particularly when it is desired to cause the solution to react in a particular manner. For example, heat is applied to a solution to initiate the polymerase chain reaction (PCR) which is used to amplify DNA fragments in the biotechnology field.
Such reactions may involve different enzymes and variations in temperature as well as extended reaction times of, for example, between four and five hours. The heating may be effected by hot water, radiation heat or other heating apparatuses.
During such processes, it is undesirable to permit any evaporation of the solution from the vessel. For this reason, a non-volatile liquid, such as mineral oil with a specific gravity of a value less than that of the solution, is added to the vessel to cover the solution so as to prevent evaporation. Alternatively, it is common practice to reduce the volume of solution that evaporates by inserting an inner cover of a predetermined size in the upper cover of the reaction vessel.
However, these techniques have their own drawbacks. It is troublesome to remove the non-volatile liquid such as mineral oil from the solution after the reaction. Impurities contained in the solution may block the occurrence of the reactions. The location of the inner cover determines the volume of solution that may be accommodated. SUMMARY OF THE INVENTION
The present invention is directed to a reaction vessel that prevents the evaporation of the solution or fluid undergoing the reaction. The reaction vessel defines an inner passage that gradually converges from an open end to a closed end. The open end preferably is closed by a cap having an opening, through which extends a piston rod. A piston head is attached to the end of the piston rod and sealingly engages with the vessel body wall in an airtight manner as it is pushed further into the inner passage. If desired, the rod and opening may be configured to frictionally engage each other to help retain a piston head at a desired relative location within the inner passage.
The bottom of the inner passage has a diameter that is smaller than the uncompressed diameter of the piston head and the top of the inner passage has a diameter that is larger than the uncompressed diameter of the piston head. As a result, the piston head, which is preferably elastic, deforms under compressive forces as it is pushed from the top toward the bottom of the inner passage and sealingly engages with the vessel body wall. By positioning the piston head adjacent to an upper surface of the fluid, evaporation of the fluid is prevented during subsequent heating and reaction of the fluid.